Refrigerated display case



Jan. 10, 1961 INVENTOR WA Y/VE H. DETW/LER ATTORNEY United States Patent REFRIGERATED DISPLAY CASE Wayne H. Detwiler, Philadelphia, Pa., assignor to C. V. Hill & Company, Inc., Trenton, NJ., a corporation of New Jersey Filed Feb. 26, 1958, Ser. No. 717,700

1 Claim. (Cl. 62-256) This invention relates to self-service refrigerated display cases and is directed particularly to constructions which are highly efficient in operation and capable of being defrosted in a relatively short period of time.

In operating self-service refrigerated display cases which are open at the top for access to customers, the problem created by the accumulation of frost on the coils and fins of the evaporator is very troublesome. This is particularly true when the equipment is operated at temperatures much below freezing, since frost often accumulates on the blower used to circulate air through the case interfering with its operation. It is also found that frost and ice which accumulate on drip pans, drains and elsewhere during refrigeration, or as an incident to defrosting, can only be melted relatively slowly when using present systems of operation. As a result the defrosting cycle sometimes must be prolonged sufficiently to endanger the articles on display.

In accordance with the present invention, these objections and limitations of prior art constructions are overcome and means are provided for increasing the efiiciency of the refrigerating operation and for speeding up the defrosting cycle.

These results are preferably attained by forming the evaporator in two separate portions, one of which serves primarily to reduce the moisture content of the air being circulated, while the other portion of the evaporator serves primarily to reduce the temperature of the air. A blower is located between these portions of the evaporator whereby the air coming into contact with the blower is relatively dry and the formation of frost on the blower and adjacent surfaces is reduced. The blower preferably also is arranged to direct air against surfaces which have ice or frost thereon so as to aid in melting the same during the defrosting cycle.

The construction further is characterized by the use of the blower to create turbulence in the air passing to the second portion of the evaporator and by the construction andarrangement of the latter portion of the evaporator so as to increase its efiiciency and develop streamlined flow of the refrigerated air passing over the walls of the case whereby heat losses through the walls are reduced.

The principal objects of the present invention are to increase the efliciency of the refrigerating cycle in selfservice refrigerated display cases and to aid in the melting of frost during the defrosting cycle of operation.

A particular object of the invention is to reduce the moisture content of air passing to a blower circulating air through a display case and to increase the turbulence of air flowing over a portion of the evaporator employed for reducing the temperature of the air.

Another object of the invention is to provide a refrigerated display case with an evaporator divided into two portions with a blower located adjacent and between the portions in position to draw air over one portion of the evaporator and to force air over the other portion.

A further object of the invention is to provide a refrigerated display case with a blower for circulating air Patented Jan. 10, 1961 through the case and arranged to direct such air against surfaces upon which ice or frost may accumulate to aid in melting the same during the defrosting cycle.

These and other objects and features of the invention will appear from the following description thereof in which reference is made to the single figure of the accompanying drawing.

The drawing is a vertical sectional view through a typical form of refrigerated display case embodying the present invention.

In the construction chosen for the purpose of illustrating the invention, the case is provided with an insulated bottom 2, insulated front and rear walls 4 and 6 respectively and insulated end walls one of which is shown at 8. The bottom and the walls of the case cooperate to define a display space 10 which is open at the top for access to customers. A rack or support 12 is located in the lower portion of the display space for receiving articles to be refrigerated.

The bottom of the display space 10 is closed by a partition 14 which is spaced from the bottom 2 of the case so as to provide an air passage 16. A cold air duct 18 is located adjacent the rear wall 6 of the case and communicates at its lower end with one end or the rear side of the air passage 16, whereas the upper end of the cold air duct communicates with the display space 10 near the top thereof. A return air duct 20 is located adjacent the front wall 4 of the case and communicates with the display space adjacent the top thereof while the lower end of the return air duct communicates with the other end or front side of the air passage 16 adjacent the bottom of the case. The air passage 16 and the ducts 18 and 20 preferably extend substantially the full length of the case and operate to maintain uniform flow of air about and across the upper. portion of the display space.

The evaporator employed for refrigerating the air being circulated is divided into two portions indicated at 22 and 24 which are located in the air passage 16 beneath the partition 14. A blower 26 is also located in air passage 16 and is positioned in a well 28 between the portions 22 and 24 of the evaporator.

The portion 22 of the evaporator is located near the front of the case adjacent thelower end of the return air duct 20 and embodies coils or tubes 30 having fins 32 thereon which extend generally parallel to each other from the front toward the rear of the case. The fins 32 are spaced apart a suitable distance to prevent clogging of the space between the fins by the accumulation of frost or ice thereon. Ordinarily the fins should be spaced apart a distance of about one-half to one-third of an inch,

The portion 24 of the evaporator is located near the rear of the case and preferably extends generally vertically with its upper side communicating directly with the lower end of the cold air duct 18. The portion 24 of the evaporator embodies coils or tubes 34 having fins 36 thereon which extend parallel to each other and in a vertical direction. The fins 36 are preferably positioned much closer together than the fins on the portion 22'of the evaporator and may be only one-fourth to one-eighth inch apart. This relatively close positioning of the fins 36 is made possible by reason of the fact that little or no frost or ice will accumulate thereon during operation of the case.

The blower 26 is mounted within the air passage 16 by means of a plate or support 38 which extends across the well 28 which forms a part of the air passage. The

blower is preferably positioned below the level of the the air flowing over portion 24 will be received from the blower and will flow upward through the portion 24 of the evaporator to the cold air duct 13.

In operating the ,dispLay case described, refrigerant is supplied to both portions of the evaporator in any suitable manner. As shown, the refrigerant is supplied by a compressor 42'located beneath the bottom. of the case and in front of the well 28 of the air passage 16. The refrigerant preferably flows through the ,coils .of evaporator portion 24 and then passes in series through the coils of evaporator portion 22. However, the direction of flow of the refrigerant may be reversed and, if desired, each portion of the evaporator may be supplied with refrigerant from a separate compressor.

The air is circulated through the case and over both portions of the evaporator by the blower 26. During such flow the air is drawn downward through the return air duct 20 and over the portion 22 of the evaporator whereby it is cooled and moisture is condensed on the coils 30 and fins 32. The moisture will ordinarily be frozen into frost and the air is so dried that but little or no frost will accumulateon the blower and surrounding surfaces. Moreover, the blower, in directing the air downward in the well 28, causes it to impinge on the bottom and side walls of the well so as to deposit any entrained moisture on these surfaces.

The blower also serves to agitate the air vigorously so that it is in a highly turbulent condition as it passes to the portion 24 of the evaporator. Such turbulence serves to increase the rate of heat exchange between the air and the coils and fins of the portion 24 whereby the efiiciency of heat exchange of the latter portion of the evaporator is materially increased. Moreover, the relatively great surface area of the closely positioned fins 36 on the tubes 34 serves to reduce the temperature of the air more rapidly and effectively than would be possible if the fins were spaced farther apart. The close positioning of the fins is nevertheless permissible in the portion 24 of the evaporator by reason of the drying action of the portion 22 of the evaporator and theextraction of entrained moisture from the air by the action of the blower.

The closely positioned fins of evaporator portion 24 suppress the turbulence of the air flowing thereover and, therefore, the air issuing from said portion andfiowing upward through the cold air duct 18 is substantially streamlined. Furthermore, the portion 24 of theevaporator is aligned with the cold airduct so .that the highly refrigerated but non-turbulent air will absorb very little heat from the rear wall of the case. The heat losses through the wall of the case are, thus materially reduced.

The air issuing from the upper end of the cold air duct 18 flows forward across the top of the display space to the upper end of the return air duct 20 establishing an effective air curtain which shields the articles on dis play from the warm moist air above the display space. The moisture and warm air which does diffuse downward into the air current and that introduced when customers reach into the case, is carried off with the return air so that its moisture is deposited on the frost accumulating first portion 22 of the evaporator. The high efficiency rear portion 24 of the evaporator is thereby shielded from moisture and the accumulation of frost thereon.

In order to defrost the evaporator heating elements such as those indicated at 44 are applied to the portion 22 of the evaporator or in a position to heat the air passing thereover. The frost and ice thus melted flow into the well 28 and are drained off through the drainpipe 46. However, the bottom and side walls of the well 28 are a considerable distance from the heating elements 44,

whereas the use of additional heating element about the well would add considerably to the cost of construction and operation of the defrosting means and would further serve to raise the temperature of the air to a point where the articles on display may be melted or otherwise damaged. Moreover, slivers or sheets of ice falling from the evaporator portion 22 and passing into the well are only melted very slowly.

In the present invention, the positioning of the blower so that it directs air downwardly against the bottom and side walls of the well serves to cause the air heated by elements 44 to impinge directly against any ice accumulated in the Well whereby the ice is melted rapidly and the time required to complete the defrosting operation and insure melting of all ice and frost is considerably shortened. Furthermore, the highly efficient heat transfer afforded by the evaporator portion 24 serves to restore the air being circulated to the desired low temperature after defrosting much more rapidly than would be possible if the fins of portion 24 were spaced apart the usual distance required when frosting of the fins occurs.

The construction thus provided is of particular value in those refrigerated display cases which are operated at very low temperatures, as when preserving and displaying ice cream. However, the construction is also of value in maintaining higher temperatures in the case. as when displaying meats, vegetable and dairy products.

The particular form of construction and arrangement of the elements employed in carrying out the present invention may obviously be varied considerably. In view thereof it should be understood that the particular embodiment of the invention shown in the drawing and described above is intended to be illustrative only and is not intended to limit the scope of the invention.

I claim:

A refrigerated display case comprising an insulated bottom and insulated front, rear and end walls cooperating to define a display space open at the top for access to customers, a cold air duct extending upward adjacent one wall of the case and having an air outlet communicating with the display space near the top thereof, a return air duct extending upward adjacent an opposite wall of the case and having an air inlet communicating with the display space near the top thereof, an air passage located adjacent the bottom of the case beneath the display space and communicating with said cold air duct and said return air duct, and means in said air passage for refrigerating and circulating air through said ducts and display space including a first portion of an evaporator located in said passage adjacent said return air duct, a second portion of an evaporator located in said air passage adjacent the cold air duct, a well in said air passage between said portions of the evaporator in position to receive frost and condensate from the evaporator, means for defrosting the evaporator located adjacent the first portion thereof, and a blower positioned in the well and directing air downward against the bottom of the well, said blower serving to draw air through the return air duct and over the first portion of the evaporator and to force air over the second portion of the evaporator to the cold air duct.

References Cited in the file of this patent UNITED STATES PATENTS 2,127,991 Candor Aug. 23, 1938 2,444,593 Davis July 6, 1948 2,513,675 Quillen July 4, 1950 2,669,850 Bishop Feb. 23, 1954 2,706,387 Swanson Apr. 19, 1955 

